Electrical system



May 22, 1945. ,1 1 KENNEDY Re. 22,643

ELECTRICAL SYSTEM original Filed Dec., 6. 1940 l y A,

\,H E ND N INVENTOR ifo/iz J Kennedy n -df .BY 1

Reissued May `22, 1945 ELECTRICAL SYSTEM John J; Kennedy, New Haven, Conn., assigner to The Safety Car Heating and Lighting Cornpany, Inc.. a corporation of Delaware Original No. 2,311,340, dated February 16, 1943,

Serial No. 368,801, December 6, 1940. Application. for reissue January 18, 1945, Serial No.

This invention relates to the translationof power'from one form to another and more particularly to a system for supplying current to fluorescent lights on railway cars where direct current is translated into alternating current of constant voltage.

An object of this invention is to. provide a reliable and dependable source of alternating current of constant frequency and voltage. A further object is to provide a motor alternator set which will start quickly and build up the output voltage rapidly'and which will maintain substantially constant voltage even 'thoughthere are wide variations in the conditions ofv use. A further object is to provide a control system for a motor alternator set which will automatically regulate the set to compensate for changes in invention, the electrical system of a railway car is diagrammatically shown with certain details omitted for purposes of simplicity. On railway cars, such as coaches, Pullman cars and the like, each car is provided with its own electrical system,` and this system generally includes a set of storage batteries, lighting and other equipment, and an axle-.driven generator to supply power for the' equipment and for charging the batteries.

the power supply as well as changes in the load.

A still further object is to provide a source of supply for alternating current power which consumes power only when in use, but which may be conditioned for use in a .minimum period of time.

Additional equipment is provided under some circumstances for supplyingy power to the system when the car is stationary, and in some systems means is provided for driving air-conditioning equipment directly from the caraxle when the car istraveling at the proper speed. Equipment for railway cars should be eflicient and dependable aswell as light in weight and sturdy inA construction. Furthermore, it is diflicult to insure that the equipment will receive proper attention during use, and it is therefore desirable that theequipment operate with a minimum of adjustment and repair.

Another object is to provide apparatus of the above character which is inexpensive to `manu facture and eilicientin operation and which is simple and sturdy in construction. A further object is to provide apparatus of the above character which islight in weight and dependable in operation, and which is readily adaptable for use under a wide variety of conditions. A fui'- ther object is'to provide a method of operating and controlling apparatus ofthe above character. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements. arrangements of parts, and in the several steps and relation and order of each of the same to one or more of the others, all asv will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

The single figure of the drawing is a circuit diagram of one embodiment of the invention Y with certain details omitted for clarity;

I'he present application relates to my copendlng application, Serial No. 340,031, filed June 12. 1940, entitled "Electric system and also relates to the copending application of Louis H. Von Ohlsen and myself, Serial No. 345,118, viiled July l2, 1940, entitled "Electric system. Material is shown and claimed herein which is not covered in those applications.

In the illustrative embodiment of the resent With the development of fluorescent lights, it has been found desirable to provide for their use upon railway cars by furnishing a reliable and eilicient source of alternating current on each car. If an axle-driven alternator were provided, it would not operatewhile the car was stationary or running at a slow speed, and when operating, the frequency of the output voltage would vary over too wide a range to be practical.

lOther systems have been investigated. and it has been-found that highly satisfactory results 'are obtained by providing an alternator driven by a direct current motor which derives its power from the battery-generator vsystem of the car As outlined herein and in thev copending applications referred to above, in providing this type of system' a'number of problems were encoun-l tered, and an object of the present invention is to overcome certain of these problems. Among the problems involved is that there is a wide variation in the voltage of the battery-generator system, as this voltage varies depending upon the condition of charge of the battery and upon whether or not power is being supplied by the generator. During normal operation of the usual type of car system the voltage may vary between 28 and 45 volts.

, In the copending applicationsV referred to above, systems are provided for maintainingsubstantially constant frequencyv and voltage of the output with wide variations in the voltage of the source and the load. Under some circumstances, it is desirable that the output voltage load and in the voltage source..

` formed which are connected in parallel across .lines 8 and I4.

build up at a rapid rate when the set is started, and then that-the output voltage be maintained within a very narrow range even though the operating conditions tend to cause va variation. In the illustrative embodiment of the present invention these results are obtained by a. motorblternator set. An alternator is driven by a direct current motor which starts rapidly because of the use of a starting Winding, and the heavy starting current is effective to cause the alternator voltage to build up at a rapid rate. When the-set comes up to speed, the starting winding on the motor is relatively ineiective and the motor tends to maintain its speed substantially constant, even though there are variations in the Furthermore, when the alternator voltage reaches the desired value, it is automatically maintained 'within permissible limits with the motor armature current increasing the magnetic'eld of the alternavided with 'a controller 4 which maintains they proper current in the generator field 6. One side of the generator is connected through a line I -and an automatically operating switch I `to a line II and a set of batteries I2; this line II is connected through a manual switch 8 to a line 8. The othersideof the generator is connected The magnetic section of the motor I8 is liberal in design and operates below 'the saturation point on the magnetization curve of the iron. Thus. an increase in iield current is accompanied by a substantially proportionate increase in magnetic flux. The Thyrite resistancejunit-s have the characteristic that their conductivities vary with the potential impressed' upon them, and when there is a variation in the voltage impressed upon substantially greater increase in the eld current,

and inthe magnetic flux, and this increase in magnetic ux is 'suiicient to hold the motor spee`d constant.

As explained in detail in the above-mentioned patent, Thyrite resistance units have a negative resistance-temperature coeiiicient, and units 42a, 42h, 42c-and 42d are so designed and positioned Vthat the changes in resistance due to temperature through a line I4-to the other side of the `batteries. Lines II and I4 are the main power lines of 4vthe battery-generator system which carries a load I6 consuming direct current. When switch 9 is closed, the voltage across lines B and I4 .is the same as that of lines II and I4, and thisvvoltage varies depending upon the state of charge of the l set of batteries and the starting and stopping of the charging action of the generator. Connected across lines 8 and I4, and -thus adapted to be energized by the voltage of the battary-generator system, is a direct current motor ls having a main shunt nerd winding l1, a starting winding I9 for producing high starting torque and an 'armature 20. The main shunt iield winding I1 is in the form of four separate winding units, designated I'Ia, IIb, IIc and I1d, and these units cooperate in producing the main magnetic field for the motor. Armature is connected through a shaft 22 to drive the armature 24 of an alternator indicated at 26 and having a main field winding 25and an auxiliary field winding21. Thev alternator output brushes are connected toa .pair of alternating current lines 28 and 3D which supply alternatingcurrent to a load 32 which, in this embodiment, is a bank of iluorescent lights and their attendant auxiliaries.

Motor IBtends to operate at constant speed throughout a wide range of variation in the supply voltage and, illustratively, this motor is of the type shown in United States Letters Patent 2,134,900, Louis H. Von Ohlsen. Accordingly, the main eld windingv I'I` is connected in series with two pairs of resistance units designated 42a, 42h,

42o land 42d, which are Thyrite resistorsforany l other material having similar voltage and current characteristics. Winding units ITa. and IIb are connected in series with resistance units '42a and 42h, and winding units I 1c and I'Id are connected in series with resistance units 42e and in this manner two series circuits are changes compensate for changes in resistance in the iield winding I1. As pointed out above, the main iield winding I'I is divided into four sepa rate winding units which are evenly spaced about the motor casing, and the Thyrite units 42a, 42h, 42c and 42d are also evenly spaced as they are c mounted on the four arms of the motor frame.

Thus, in the resistor units, heat is produced and is readily dissipated the same as in the field windings, and the proper iield current iiows at all times.

When itis desirable to provide alternating current, switch 9 is closed, and it is important that upon the closing of` switch 9, power will be available without undue delay. Motor I8 is therefore provided with a starting Winding I9, which is so designed as to make the' motor start rapidly. Furthermore, as the motor starts, the alternator voltage builds up rapidly due tothe fact that the auxiliary field Winding 21 of the alternator 26 carries the full ycurrent of the motor armature.

That is, the starting current is substantially 1 field winding producing the effective portion of the eld iiux When the motor is operatingat full speed.

When the motor isl running at full speed, a change in load causes a change in the armature current which iiows through Winding I9, and due to the unsaturated condition of the iron parts of the motor these variations in current tend to cause variatonsin the field flux. This is. un

f desirable particularly becauseoi" the fact that variations in eld flux have an inverse eii'ect upon motor speed. That is, an increase in loadtends to cause an increase in this ii'eld flux,l which in turn tends to cause a decrease in motor speed, and conversely, a decrease in load tends to cause an increase in speed. In addition to the effect of winding I9,xan `increase in the mechanical load Anals of a rectifier unit 1li.l connected through leads 82 and 8l to the output which opposes the main motor field winding 4I`|,-

and the starting winding I9. Winding 5I derives` its power from the alternator output and is connected through leads 52 and 54 to a rectifier unit 55. Rectifier unit 56 has its input leads 53 and 55 connected to the output terminals of the secondary winding 58 of a current ltransformer Ell. 'I'he primary winding 62 of current transformer III is connected-in line 30 of the alternator load circuit. During the startingperiod of the motor alternator, and until there is a-load on the alternator, there is no current flowing through line 30, and therefore no current is supplied to winding Vmum running temperatures.

5|, with the result that starting winding I9 and e the main field winding. I1 produce the'en'tire field flux. When there isa load on alternator 26, a proportionate current is delivered through transformer i0 and rectifier unit 56 to winding 5I and this current tends to oppose the eect of field windings I9 and I1. The effect of this current in winding 5| is sufficient to neutralize winding I9.

and other factors, such. as armature resistance, etc., which tend to reduce the motor speed.

kThus,'the compensating field winding reduces the total field flux produced'by allof the motor .field windings to maintain constant motor speed.

In the present embodiment the main alternator field winding is supplied with current which is derived from the output circuit'of the alternator. Accordingly, the transformer 12 has one side of its primary 1l connected through a lead 16 to line 2l andthe other side of the primary is connected through a line 18 to line 30. The secondary winding 80 is connected across input termi- Field winding 25 is terminals of the `rectifier units with the resistance unit 36 connected in lead 8l in series with the` field winding. Resistance unit 36 has a zero temperature-resistance coefficient so that it reduces the'eiiect which'changes in temperature of the field winding have upon the total resistance of the circuit.. The iron core of alternator 26 is not saturated magnetically, and during operation field windings 21 and `25 cooperate to produce magnetic flux suiilcient to maintain constant e voltage.' These two field windings are in the form ofseparate sets of windings which are mounted together.

During the startingperod the heavy starting current of the motor iiowing through field Winding 21 sets up a strong magnetic field which is effective to make the alternatorv voltage build up rapidly. After the set begins to attain speed. the armature current of the motor drops off rapidly, but at this time the alternator voltage is of sui'- ficient value to cause winding 25 toproduce a strong magnetic flux. Thus, the voltage is quickly stabilized and thereafter the constant voltage of the alternator causes'the field winding 25 to produce a constant flux. When a load is placed on the set, there is an increasein the amature current of the motor, and the various parts are so Vmaximum voltage of 128 volts when the set was operated throughout the range of extreme conditions. These extreme conditions included a change in load from no load to 1 250 watts with the direct current source at the extreme voltages of 28 volts and `45 volts, and with the temperature of the set varied from minimum to maxi- With this narrow range of variation under these extreme conditions, it is readily seen that during normal operaytion the variation is much less.

As many' possible embodiments may be' made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing fromthe scope of the invention. it is to be'understood that all matter hereinabove set forth. or

' shown in the accompanying drawing is to be interprcted as illustrative and notv in a limiting sense,

I claim: 1. In arailway car electrical system for supplying alternating current of substantially constant frequency and voltage wherein power is available `from a battery-generator system, the combination of: a direct current motor having an armature and a set of iield'wndings including a main motor winding and a starting winding: means connecting said'starting winding in series with said armature; means connecting said main motor winding to receive current from the battery-generator system with control means to regulate the current to maintain substantially constant motor speed throughout a permissible variation in the supply voltage; an alternator having an armature, a main alternator field e winding and an auxiliary alternator field winding; a rectifier unit; means connecting said auxiliary alternator eld winding in series with the armature of said motor to thereby provide a heavy magnetic field for the alternator during the starting period; means connecting said main alternator field winding to the outputv terminals of said rectifier unit and connecting the input terminals of said rectifier unit to receive power from the output of said alternator so that said -main alternator field winding produced magnetic flux which varies' with the output voltage of the alternator. v

2. In a railway car electrical system for supplying alternating current of substantially constant frequency and voltage wherein power is available from a battery-generator system, the combination of: a direct current motor comprising, a main motor field winding; a starting winding, an auxiliary motor field winding, and a motor armature; an alternator comprising a main al ternator field winding, an auxiliary alternator field winding, `and an alternator amature proportioned and adjusted thatl the voutput voltage of the alternator is increased suiflciently to overcome the voltage drop across lines 2B and 30 mechanically connected to said motor armature; means electrically connecting said starting winding and said auxiliary alternator field winding in series with lsaid motor armature: means including a resistance -asser'nbly electrically con-4 nected in series with said main motor eld winding across said battery-generator system, saidresistance assembly having the characteristicthat its resistance varies with the voltage impressed across it so thatthe motor speed tends to remain constant wtih changes in the supply auxiliary motor winding receiving current so that it tends to set up a magnetic ilux opposing the main eld nux of the motor with the value of current varying with the load on said alternator, and said auxiliary alternator winding 'receiving i current so that it assists -said main alternator iield winding in producing the magnetic eld for the alternator. H

3. .In an electrical system for supplying power to a load the characteristics of which may vary wherein power is derived from a variable source, the combination of, a constant speed motor having ileldwindlngs and means to maintain substantially constant speed with variations in the voltage of the variable source, a generator mechanically connected to be driven by said motor and having its output leads connected to supply power to the load, said generator having a main eld winding connected to receive substantially constant current from said output vleads and anauxiliary winding connected to carry current which varies with the load, and a compen- `eating winding for said motor connected to carry current which varies with the load to thereby compensate the speed of the motor for load variations.

ings and means to maintain substantially constant speed with variations in the voltage cf the variable source, an alternator mechanically connected tovbe driven by said motor and having its output leads connected to supply alternating curnected to be driven by saidmotor and having its output leads connected to supply alternating current power to the load, said alternator having a rectifier means and a main iield winding connected through the rectier means to receive subs,

stantially constant current from said output leads and having an auxiliary winding connected -to carry current which varies with the load, and

thereby to compensate the speed of the motor for load variations. A

6. In a railwayv car electrical system for supplying alternating current power of Substantial- .ly constant frequency and voltage to a load the' characteristics of which may vary wherein power is derived from a variable source, the combinaofthe variable source, an alternator mechanically connected to be driven by said motor and having its output leads connected to supply alternating current power to the load, said alternator having a main field winding connected to receive substantially constant current from said output leads and having an auxiliary winding con- Y ne'cted to carry current which varies with the load, and a compensating winding for said rnc-- tor connected to carry current which varies with f the load thereby ito compensate the speed 'of the motor for vloa'd variations.

7. In a railway car electrical lvsystem for supplying alternating current power of substantialn ly constant frequency and voltage to a load the rent power to the load, said alternator having v la main field winding connected to receive substantially constant current from said output leads and having an auxiliary winding .connected to carry current which varies with the load, and ,a compensating winding for said motor connected to carry current which varies with the load thereby to compensate the speed of the motor for load variations.

5. In a railway car electrical system for supplying alternating current powe of substantially constant frequency and volta to a load the characteristics of which may vary wherein power is derived from la battery-generator system the voltage of which varies, the combination of, a constant speed motor having field windings .and means tomaintain substantially constant speed with variations-in the voltage of the battery-generator system, an alternator mechanically concharacteristics of which may vary wherein power is derived from a Variable source, the combination of, a constant speed motor having eld Windings and means to maintain substantially constant speed with variations in. the voltage of the variable source, an alternator mechanically connected to be driven' by said motor and having its output leads connected to supply alternating current power to the load, said alternator having a mainiield Winding connected`toreceive substantially constant currentfrom said output 

